1. Technical Field
The present invention relates to a reduced-pressure drying method for drying a base material coated with a liquid substance under reduced pressure to form a film on a surface of the base material, a method of manufacturing a functional film, a method of manufacturing an electro-optic device, an electro-optic device, a liquid crystal display device, an organic EL display device, and an electronic apparatus.
2. Related Art
A reduced-pressure drying method using a reduced-pressure drying device, which is used for forming a film on a surface of a wafer-like substrate (base material) made from, for example, semiconductor by applying a liquid substance including film forming material and is capable of drying the substrate by evaporating a fluxing material (solvent) included in the liquid substance under reduced pressure, is known. For example, in JP-A-2004-47797, there is proposed a reduced-pressure drying device provided with an airtight container for keeping a substrate coated with a coating liquid (photoresist) under reduced-pressure atmosphere, an evacuating means for evacuating the airtight container, and a current plate having a size equal to or larger than the effective area of the substrate and disposed in the airtight container so as to face the substrate.
Further, as a reduced-pressure drying method using the reduced-pressure drying device described above, there is proposed a reduced-pressure drying method including the step of disposing a current plate so as to face, with a gap therebetween, a surface of a substrate mounted on a substrate mounting section provided inside an airtight container, the step of evacuating the airtight container up to the pressure with which a solvent component is rapidly evaporated from a coating liquid, and the step of changing a setting value of an outlet flow to at least two stages while the solvent component is rapidly evaporating from the coating liquid.
In such a reduced-pressure drying method, by changing the setting value of the outlet flow while the solvent component of the coating liquid is rapidly evaporating, a stage in which the solvent evaporates at a high rate and a stage in which the solvent evaporates at a low rate are combined, thereby correcting a cross-sectional shape of the coating film in the periphery of the substrate. Thus, an outlet flow pattern capable of obtaining a planarized coating film with in-plane uniformity can allegedly be set with ease.
As described above, in manufacturing processes of a majority of electronic devices such as semiconductors, there is adopted a process for forming a coating film (a functional film) composed of various kinds of film-forming materials on a surface of a base material such as a wafer by applying a liquid substance containing the film-forming materials (functional materials) on the base material.
However, in the drying process for forming the coating film by drying the liquid substance, it is quite difficult to dry the liquid substance so as to obtain a resulted coating film more even and having an even film thickness distribution throughout the whole surface of the base material, even by using the reduced-pressure drying device and the reduced-pressure drying method described above. Because, the liquid substance is of great variety, and the saturated vapor pressure and the rheologic properties (properties such as viscosity, elasticity, plasticity, or thixotropic property) vary by each of the materials. Further, a behavior of the liquid substance in the drying process such as the evaporation rate also varies by the volume ratio or the surface area ratio between the solute and the solvent included in the liquid substance.
Therefore, even if the rate of evaporation of the solvent from the liquid substance under the reduced pressure is controlled by changing the setting of the outlet flow using the reduced-pressure drying method of the related art described above, a fluidity (convection) of the liquid substance occurs in the drying process, thus the evenness of the film thickness is problematically degraded by the surface tension thereof. Further, even if the direction of solvent vapor ejection is controlled by the current plate, since the vapor density (or the vapor pressure) distribution is different between the central portion and the peripheral portion of the base material, as a result, in-plane distribution of the film thickness is problematically caused by the difference in drying rate.